1. Field of Invention
The present invention relates to insoles for footwear and more specifically to a method for computer aided design and manufacture of custom pressure reducing insoles for footwear.
2. Background of the Related Art
It is generally known that high plantar pressures under the foot can lead directly to undesirable injury and symptoms in the foot. Such injury or symptoms may include pain in a foot with sensation, or tissue damage and ulceration in a foot without sensation. As a result, reducing pressure at identified high pressure locations is believed to offer a therapeutic strategy for treatment of foot disorders.
In the past, insoles for footwear have been used to reduce pressure at presumed or identified high pressure locations. Custom and customized footwear insoles (where the term “custom” is used to mean both fully custom and modified off the shelf footwear insoles) are believed to provide improved pressure reduction over flat insoles and this has indeed been demonstrated by recent research. Manufacturing of such custom insoles is generally performed by trained pedorthists/orthopaedic shoemakers, who customarily use a negative mould of each foot for obtaining the desired base shape of the insole, to which they then make primarily subjective modifications to off-load the presumed or identified high pressure locations. Due to its subjective nature, this process has been shown to yield inconsistent results with respect to obtaining the desired pressure reduction and, because the process is labor intensive, it is expensive.
Computer aided manufacturing using numerically controlled machines is also possible, as disclosed in U.S. Pat. Nos. 5,088,503 and 6,804,571. Such systems have provided some of the measurements necessary to determine the high pressure locations to be accommodated within the insole to be designed. However, such systems have failed to provide the necessary combination of measurements to accurately align the high pressure locations or other locations of interest on the subject's foot with the insole to be designed and manufactured, in order to obtain precise and reproducible insoles from the measurements obtained. They have also not provided an approach to determining pressure regions and deciding the regions of interest based on a method of “thresholding” these regions based upon measured plantar pressure data. Such patented systems also suggest that footwear should reduce pressure distributions toward some ideal value but research has shown that the considerable variability in human feet makes such a concept untenable. The improvements provided by the present invention overcome these prior difficulties and result in an improved method and system for producing an improved pressure reducing insole.